Electric incandescent lamp



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bw/ T J. E. STONE ETIAL ELECTRIC INCANDESCENT LAMP Flled July 1 1950 July 29, 1952 Patented July 29, 1952 r H ELE'oTRi'oINoANDEscENT'LAMP' Joseph Ston'e; Cleveland Heights, and John 0.

Geissbuliler, So1ith-Euclid,;-0hi0', assignors to General: Electric Compannwe corporation of New York Application may 1, 1950; ethane-171.7 68

' 1 Our invention" relates in general to electric in-- candes'c'ent lamps, and more particularly-to a reflector type incandescent lamp adapted to pro j'ect a concentrated light beam of high intensity. Reflector type electric incandescent lamps of the so-called sealed beam type described and claimed in U. S. Patent 2,l"48,3'l4D. K. Wright, and comprising glass reflector and cover glass sections fusion-sealed together to formthe lamp envelope and having aconc'entrated light source located at or closely adjacent thefocus of the reflector are well known in themselvesand 'arein widespread use in many applications as, for example, in vehicle headlights, airplane landing lights, fioodlights and spotlights, tofmention afew. 'Another useful application is for a small portable spotlight or as a spotlight for general service, such as store lighting and displayff'or instance, which is operable from a commercial power line and is capable of projecting an intense light beam over an extended distance. A lamp suitable for such spotlight use is described and claimed in copending U. S. application Serial No. 171,726, R. E. Smith, filed of-evendate herewith and assigned to the assignee of this invention, now U.- S. Patent No. 2,597,681, issued May 20", 1952. The present application relates to animprovement over thelamp construction disclosed inthe aforesaid copending application. It is an object of ourinvention to provide an electric incandescent 'lamp of the above-mene tioned sealed beam type which willproduce a concentrated high intensity light-beam which is of more or less circular cross section with a central hot spot of maximum beam candle power and which uniformly tapers off in intensity to the outer edges oi-the 'beam so as to be free of-dark spots therein. Another object of our invention is toprovide a relatively high wattage electric incandescent lamp of the above character which isoperable from a commercial or household power source and which" will producea concentrated high intensity light beam of more or less circular cross section: and ofgreat projectiondis-tance; Still another object of our invention is-topro vide anel'e'ctric incandescent lamp of the above character having ai 'three segmentfilamenti and whichis of simplified and: rugged construction and 1S capable of withstanding impactsor sudden jars without *breakageof the filament" or" dis-tore tiori thereof which would" result" inpremature mam t hurn outand shortened'lamp' life'.

" urtherobject of ourihi ntidn is' to provide an electricincandescentl'arnpofthe above char= =liavirrg a filament which: is concentratedfo cal point or the focusing reflector of, the p envelope and which is efiectively-suppor'tei to protect it against physical shock and maintain it' in proper positionsubstantially free from: sagging during operation.

Acc(Jr-ding to one aspect of the inventioma coiled-coil ti'ingsten' wire filament of. proper length and resistance for operation from an ordicommercial or household power line of from -120 volts; for instance. is dividedinto :three individuat leg portions or segments the center one ofwhich is longer than" the two endsegments, wh'i h 'segmentsparedisposed in a Single plane and at an acute" angle to one another'to form an N or Z shape-,2 and the so-for'med filament isiar: ranged: substantially symmetrically about. the focal point of the focusing reflector of a .fs'ealed beam type lamp such. as disclosed in the' abovementione'd ll. S. Patent'2,148',314, with the plane of thefilament l'ocated in an; axial plane of the reflector axis and therc'enter segment of the filarrient extendings'along. the axislof the reflector. "According toanother' aspect of the invention, the above-described N or z-shaped filament is supported: in place in the lampenvelope to withstandiphysical shock and maintain its initial position free fromsagging in aniaxial'plane 0t -the' lamp" reflector by having its opposite ends ci'a pea. otherwise securely fixed tothe inner endof rig'id ii nleadi conductor-sand byfb'eing a-d diifionally supported. intermediate its length. at the big'hts T connecting? loops between adjacent coil-legs or segments by supplem'entary supports anchored to an insulating bridge fastened: across the rigid inlead conductors. Further objects and advantages of our invention} Willappear from'the following detailed description of species thereof and from the accom-v panyin'g'drawing'.

In the drawing, Fig. l is a sectional view of anele'ctric" incandescent lamp comprising our invention; Fig. Z' isan enlarged perspective view of the 'aniount' structure of the lamp shown in Fig.1; and Fig} 3 is an enlarged perspective view of a modifiedmount structure according to the invention. I

-Referfing to the drawings, the electric incandescent 'lamp' according to the invention is of the fs'eaIedb'eam type disclosed and claimed in the above-mentioned U. S. Patent-2,148,314, D. Wright, andcompri's'es a sealed glass envelopeor bulb I consisting of a preformed pressed glass refiector-section 2 and a preformed pressed glass cover section 3 fusion-sealed together at their thereabouts, so as to redirect light rays from a concentrated light source at the focus of the reflector B into a long beam of substantially parallel rays. The reflecting coating 6 may be of aluminum, silver or other similar light-reflective 7 material.

4 2!, 2i extend approximately parallel to and lie in a plane containing the axis xa: of the reflecting surface 6, and they are substantially symmetrically disposed on opposite sides of said axis. Adjacent their inner ends, the inleads 2i, 2! are symmetrically offset inwardly toward each other, by means of inwardly bent portions 23, 23, to provide inwardly offset inner ends 24, 24 lying in the same plane as the outer portions 25, of the inleads and extending substantially parallel to the reflector axis x-zc. The inwardly bent portions 23, 23 of the inleads, along with the inwardly offset inner ends 2d, 24', thus together con- Mounted on the rear outer side of the reflector section 2 at the region of the apex or center thereof is a base structure 1 of the side-prong type shown and described in U. S. Patent Application Serial No. 171,766, Geissbuhler et al., filed of even date herewith and assigned to the assignee of the present invention, and comprising a pair of terminal contacts 8, 8 in the form of metal prongs or contact blades which are rigidly secured and electrically connected at one end to the'closed nipple ends 9 of respective metal ferrules or thimbles I0, ID. The ferrules 10, ID are formed of a suitable metal which will readily wet and adhere to the glass of the reflector section 2 and they are provided with skirt portions 1 l which are feathered to knife edges embedded and fused in the glass of the reflector section 2 around respective openings or passageways I2 through the wall thereof. The contact prongs 8 are preferably secured to the nipple ends 9 of the ferrules M by being wrapped therearound and soldered thereto, and as shown, they extend laterally of the reflector section 2 and project outwardly from the side of a generally cylindrical metal cup or cap l3 which is securely fastened to the base end or apex of the reflector section to enclose the projecting ferrules ID. The contact prongs 8 are firmly held in spaced relation, insulated from each other and from the metal cap l3, by an insulative spacer block 14 of porcelain or other suitable insulating material which projects through an opening l5 in the cylindrical wall of the metal cap [3 and is slotted, as indi cated at l6, to receive and hold the prongs 8 therein. The envelope I is provided with an exhaust tubulation ll communicating with the interior of the envelope through an exhaust opening H8 in the envelope wall at the apex of thereflector section 2. After exhaustion of the en-v velope through the tubulation; l1 and, if desired, the introduction of a suitable gas filling such as nitrogen 'or argon, the tubulation I1 is sealed or tipped off as indicated at [9.

Mounted within the envelope I and supported solely from the metal ferrules Ill, [0 is a lamp mount structure 20 according to the invention and comprising a pair of rigid wire inleads 2|, 2| secured and anchored at their outermost ends within the nipples 9 of the ferrules, as by solder 2,2 as shown. The inleads 2|, 21 are made of any suitable material, such as molybdenum, nickel or iron, which will withstand the heat to which they are subjected during lamp fabrication and operation, and they are of large enough diameter to render them relatively rigid. In theparticular case illustrated, for example, the inleads; 21, 2|

are made of 50 mil diameter nickel-platediron wire. From the ferrules 10, Ill, the inleads 2!, 21 extend in more or less parallel'spacedrelationi678 inch apart in the particular case shown)v through the openings I2, 52in the wall of the reflector section 2 and into the envelope l. The inleads stitute inwardly directed and confronting inner end portions, of the inleads 2 l 2!. At their innermost ends, the inleads 2i, 2| are suitably connected, as by clamping or welding, to the terminal ends or extremities of an electric energy translation element or filament 2'5. In the particular case shown, the innermost ends of the inlead offset portions 24, 2d are flattened and reversely bent back upon themselves to form hooks or clamps 26 located substantially in the plane of the inleads 2i, 2E as'well as in the focal plane of the reflector, within which hooks the filament ends are clamped to thereby securely fix the filament ends and fixedly position and rigidly support them from the inleads in the plane of the latter, and provide a good electrical connection therebetween. The filament 25 comprises a fine tungsten wire 'of suitable design or size, i. e., length and diameter, to operate at the particular voltage and wattage for which the lamp is designed, for example, from a conventional commercial or household power line of from 110-120 volts and at a wattage of say to 300 watts, for instance, and it is coiled throughout its length into small or minute minor coils and then into larger or major coils to form a coiled-coil wire. By employing a filament in the form of a coiledcoil wire, the over-all length of the filament body is shortened to impart ruggedness thereto and concentrate it as much as possible.

The coiled-coil filament 25 according to the invention is divided into three straight leg portions or segments 27, 28, and 29 defined by the larger or major coils of the filament, which segments are arranged at an acute angle relative to each other to form an N or Z shape and are joined at the apices of the N or Z by connecting loops or bights 3i], 3i (Fig. 2), each formed by opening up one of the major or larger coil turns of the coiled coil filament wire. The angle of divergence or spread of adjacent segments of the filament 25 is preferably made relatively small or narrow to concentrate the filament about the focal point F of the reflecting surface 6, and the three segments 21, 28, 29 are disposed in a plane containing the axis of the reflector, and-preferably in that axial plane thereof which includes the inleads, in order to present the smallest possible projecting area to obstruct the light rays reflected from the central regions of the reflecting surface 6 toward the front of the envelope.

The outer segments 21, 29- of the filament 25 according to the invention are made shorter than the center segment 28, and the lengths of the said center segment and the'two outer segments, and the angle of divergence of the latter from the center segment 28 are so proportioned as to produce the optimum desired beam pattern and locate the end legs or extremities32 of the filament at points substantially midway of the length of the center segment 28'so as to lie opposite one another laterally of the center segment, In general, we have obtained good results by making the lengthiofthe outer or endi segments-52 3atleast 40-pe'r'cent; but; not more than 90 per cent, of the' length of the center segment 28; andpreferably about; halfas long asthe-cen-ter segment. In accordance w ith-the invention, the N or Z"-shape'd filamentfiis-mounted substantially symmetrica-lly orcenteredjabout the focus-of the reflecting surface 6-" with the center segment '28- extending axially o-fthe refiectorax'is m at-and its midpoint located at the focus F oi-therefiecti ng surface.

The-filament-2i is addition-ally supported at the fbights 3'0, 3 thereof to mai-ntain the-apices of the frl'ame'nt'substantially in the plane-bathe ihleads' 21 2-|-- and -hold-- thefilament-in-place against sagging- -duri'ng operation, by a pairf intermediate supports 3 3-, 34i- The said intermediate s'\ip; io1'*ts -n'ia-y be made or |'2"-mil= diameter molybdenum wire, for instance,- and they are each embedded at oneend-in'the-glas's rod 3 of an insulativebridge' or -cross bar 36 which-is fastened acrcss the two inleads- 2 2 a position wardly of the filament,- by pair's-'otsupport'wires 3T=-, 3"| extendin from the opposite-tends of the glass-roses and welded or otherwise secured-- to theinlead'sto thereby rigidly tiethe latter together; One of the intermediate filament support Wires 341s longer thanthe" other support wire-33 and it. extends rromgtne glass-insulator rod 35- in a: direction transver ely to the plane of the inleads 2|, 2'|--as indicated at38 andisthen bent to extendoutw'ardl-y of the reflecting surf ace G in; a;direction more or lessi parallel toor at a slight" angle tothe axis of. the reflector, as indicatedat 39. The freeer id of the support' wire 34 is bentlinwardly toward the filament" to form an inturnedarm 40 formed with a U-shaped loop or hook-4|: within which-theu pper bight 33 of the; filament is. loosely hooked: to thereby position andsupport the filament at its outer apex against sagging. .'Ifhe otheror shortersupport wire-33 extends from the glass insulator-routs in a direction outwardly of the reflector 2 substantially parallel to the reflector axis'i'af -rr and in-the plane ofatheifil'am'ent .25, and is likewise-provided at its free end with a vU-shap'edi loop o'r'hook 4 -2 within which the lower bight 3| of the filament is loo'sely hooked. tothereby position and support the filament .at its'='.i-nner: apex against-sagging. As

shown: the hooks '41,. 42,. on which the filament bights 30, 3| are respectively hooked, are located substantially in the common plane of the i-nleads 2h, 2 and. filament 3 25 to thereby position and support the filament at its apices, from sagging,

substantially in the plane of the inleads' 2 I, 2-|'.

The filament bights30, 3| are loosely hooked orrlooped over the U-shaped hooks 4|, 4 2 of the support wires 33, :34 in order to permit a limited amount of free movement of the filament bights in the hooks longitudinally of the filament segmentsduringoperationof the lamp to compensate for the expansion and contraction of the filament segments, and also in order to space the filament-segments, at the apices of the filament, sufficiently far apart to prevent contact therebetween whenthe lamp is subjected to a physical shock. As shown in Fig.2, the u-shaped hooks 4|, flare sufficiently deep andpractically parallet to one another to thereby 'fu'nction asguiding meansjfor the apices of thefilament and prevent displacement or disengagement of the filament from the support hooks 4|, 42 when heated during the operation of the lamp. Preferably, the intermediate filament support wires 33, 34 are initially set to exert a sufficient pull on the apices of the filament in opposite directions lengthwise (sf-the imeads 21, 2| seas-to drawthe filament.

segments mere: or less taut between their: points of supp'ort, thus tending to keepthe filamentLsubrstantially taut and tree from sagging in theplane thereotdurin'g' lamp operation so as to maintain thelight rays in proper focus relative. to the re'. hector. The intermediate supports. 33, :34fiare sufiiciently rigidto prevent. permanent displace ment of the filament from itsinitial position, but the'slightresiliency of these supports permits the filament to moveslightly when the: lamp is subz-f jected to aphysi'cal shock so. that there; isaless danger of..filament breakage thanwould .be/the case ifall strains. had to betaken: up: by each individual. segment oithe filament. I l Th'e'llmodified. mount structure: 43 illustrated. in Fig. 3E differs fromthat-shown in Figs. 1 and. 2 only in the -.form of the end 1e'gs '4 5 of. the-imament .44 I which in this. case are arranged so as to extend substantially alongthev respective axes of the outer filament segments 21,. 29;. and intheform: of. the inleacls...46-, which are bent: in ward. at their inner. ends to form inwardlyldilrected'v confronting inner end portions; 3415,- .41 which. extend: toward the reflector axis and lie in the same plane as-the main inlead portions 45,; 46. Theinn-ermost ends'ot the inleads lii 66 are formed withh'ooks. 48,48 within-whichthe filament end legs or extre'mi'tie's lt: are clamped substantially along the respective axes or the two outer segments 215, 29 of the filament, some of the. minor coils of: the singlecoiled endportions d5 of the filament. being crushed between. the two sides of the i-nlead hooks A8 in the sam manner. as in Figs. 1 and. 2.

The relatively. small angle. ot divergenc t r spread of the filament segments 21,18, 29,

'coupled'with the coi1ed-coi1 construction of-the filament, serves to concentrate-the: fiiament at and adjacent the .focal point F of the reflector 6 suliiciently so as to produce a light beam which is of. substantially circular or-slightly elliptical section and which is of maximum intensity at the. center: thereof and uniformly tapers' oft in intensity to the outer edges of the beamso; as to beifree of dark spots or areas of lower intensity in the central regions of the beam. The center segment 28 of the filament, becauseor its-disposition extending along the: axis 50-02" otthe reflecting surface 6, produces anintense spot of light at the very. center of the beam, while the two outer segments 21 and 29 produce offset spots of light which are located slightly to either side of the center or the beam depending upon the. spread. of the segments.- However, because of :the shorter length of the outer filament segments 21, v29 as compared to the center segment 28*, and their location to one side of the focus F of the reflector, the offset spots of light produced by the outer segmentsZl, 29 are not as bright as the central spot producedby the center segment 28. Consequently the light intensity or beam. candlepower tapers off or diminishes more or less uniformly from the center of the beam, resulting in a beam which is of excellent beam candlepower distribution characteristics and which," when further'coupled with a lightly Stippled or otherwise slightly diiiusing cover glass 3 to smooth out the slight irregularities in the beam, provides an exceptionally smooth beam of uniform graduated beam candlepower highest at the center and gradually decreasing outwardly thereof. This is in marked contrast to the beam produced by a V-shaped coiledcoil filament mounted symmetrically about the focus F of the reflector so as to lie in an axial plane'of the reflector with; its apex pointed outwardrandlocated on the axis of the reflector, such a beam being characterized by a darkened spot, at the center of the beam dueto theifact that, the two diverging legs of the V filament produce bright spots located slightly to either side 20f the center of the beam.

From the above description, it will be apparent that we have provided .a sealed beam type of lamp for operation from a power line of any suitable voltage, such as a conventional com- 'mercial or household power line of 110 to 120 voltsfor example, and which will operate to project a concentrated and substantially circular light beam of high intensity, and of excellent beam candlepower distribution characteristics, for a, relatively great distance. The filament is composed of three coiled-coil segments or portiong. which are arranged in the Shape ofan N or Z and which concentrate the filament so as to approximate the desired point source of light for use with the focusing reflector, and an effective supporting arrangement is provided to support the filament rigidly at its terminal extremities as well as at points intermediate its end to thereby protect it against physical shock andmaintain all portions thereof substantially in their initial position, free from sagging, in-an axial plane of the reflector during all operating conditions throughout the life of the lamp. Moreover, the construction and arrangement of the filament segments 27, 28, 29 so that the filament end legs or extremities 32 or 45 arelocated opposite one anotherapproximately midway of thelength of the center segment 28, enables the use of inleacls. 2 or. 36 of substantially identical form or shape, thus minimizing and simplifying the'manufacturing operations and the number of parts required for the mount structure according-to the invention.

construction and arrangement of parts shown,

but that they may be widelymodified within the spirit and scope of our invention as defined by the appended claims.

a 2. An electric incandescent lamp comprising a sealed envelope having a focusing reflector for producing a long beam of parallel rays, a pair of rigid inlead conductors sealed through the What we claim as new and desire to secure by 7 Letters Patent of the United States is: l. A spotlight comprisinga focusing reflector for producing a long beam of. parallel rays, a pair of rigid inlead conductors extending into the interior space of said reflector and having their inner ends disposed laterally on opposite sides of. the axis of said reflector and substantially in an axial, plane thereof, a coiled-coil filament mounted within said reflector on said conductors and comprising three individual segmentsinterconnected at their endsand arranged in substantially an N-shape, the opposite ends of said filament being connected to and supported in said plane by the inner ends of said conductors, and means for additionally supporting the filament at the junctions between the said segments to hold it substantially centered about the focal point of said reflector and substantially in said plane withthe center'segment of the filament extending. axiallyof the reflector and the midpoint of said center segment located substantially {at the focal point of-the reflector.

wall of said envelope and extending into said envelope with its inner ends disposed laterally on opposite sides of said reflector and substantially in an axial plane thereof, acoiled-coil filament mounted within said envelope on said conductors and comprising three individual segments inter-- connected at their ends and arranged in substantially an N-shape, the opposite ends of said filament being connected to and supported in said plane by the inner'ends of said conductors, and means for additionally supporting the filament at thejunctions between the saidsegments to hold it substantially centered about the focal pointof said reflector and substantially in said plane with the center segment of the filament extending axially of the reflector and the midpoint of said center segment located substantially at the focal point of the'reflector. YY v 3. An electric'incandescent lamp comprising a sealed envelope having a focusing reflector for producing a long beam of parallel rays, a pair of rigid inlead conductors sealed through the wall of said envelope and extending into said envelope in the general direction and on opposite sides of the axis 'of said reflector with its inner ends disposed substantially in an axial plane of and in the focal plane of said reflector, a coiled-coil filament mounted within said envelope on said conductors and comprising three individual-segments interconnected at their ends and arranged in substantially an N-shape, the opposite ends of said filament being connected to and supported substantially in said planes by the inner ends of said conductors, and means for additionally supporting the filament at the junctions between-the said segments to hold it substantially centered about the focal point of said refiectorand substantially in said axial plane with the center segment of the filamentextendingaxially of the reflector and the midpoint of said center segment locatedjsubstantially at the focal point of thesre flector. I 1

4. An electric incandescent lamp as set forth in claim 1 wherein the outer segments of the said filament are of shorter length than the center segment thereof. 3 a

5. An electricincandescent lamp as set forth in claim 3 whereinflthe said'additional support means comprises an insulative bridge fastened 1 REFERENCES CITED The following references are of record in the meet this patent:

UNITED STATES PATENTS,

Number 7 Name Date 2,497,566 Stone Feb. 14, 1950 2,497,567 Stone Febi14, 1950 2,508,063 Gross May 16, 1950 

